... but I don't understand why Berkey is better than other gravity systems and if they are why they refuse to document it.
All the reasonably good purifiers cost a good deal of money and I want some solid proof before I lay that much down.
I share your frustration with this lack of hard numbers from independent lab tests. Searching around just now for "berkey filter lab test" turned up a lot of drek, but it also turned up these three pages of results that seem credible.
http://www.consciouswater.ca/berkey-water-filter-test-results/https://www.consciouswater.ca/wp-content/uploads/2013/01/Black-Berkey-Virus-Bacteria-Removal-Test-Report.pdfhttps://berkeywaterfiltercanada.ca/wp-content/uploads/2015/01/county-los-angeles-inorganic-test-results.pdfLike you Justin, I wish that Berkey would be more up-front with their numbers. On the other hand I also think that
most people don't give two damns about the numbers, they just want reassurances and a shiny filter. People who'll look into the numbers will look up the numbers, but for the other 99% of the market, if you put the numbers up front their eyes will glaze over and they'll drift on to other sites. No economically feasible home filter can remove 100% all of contaminants, so that would be false advertising. If you try to say "removes 99.99999% of bacteria," they'll want to know why it doesn't remove ALL bacteria. Then, as the saying goes, if you have to explain don't bother.
BTW, I have a Berkey in everyday use. It cleans up the crappy (literally?) municipal water here; the brown tinge

is gone, and the flavor is much improved. It's worthwhile for those reasons alone. But what I really have it for is to treat whatever water's available post-next-bad-hurricane. I'm mostly worried about bacteria, but protozoa and viruses are also a concern. From everything I've seen, it'll do the job.